(1) Field of the Invention
The present invention relates to a method for producing novel dried compositions containing polysaccharides, particularly dextrans and levans. In particular the present invention relates to powdered compositions containing milk solids mixed with the polysaccharides which hydrate to form thickened aqueous solutions and which are particularly useful as edible quality improvers (e.g. stability, thickeners and/or texture) for foods.
(2) Prior Art
Dextrans are glucose polymers synthesized by several genera of bacteria including Streptococcus, Lactobacillus, and Leuconostoc (Schwartz, R. D., and E. A. Bodie, Appl. Environ. Microbiol. 48:678-679 (1984); and Lawford, G. R., A. Kligerman, and T. Williams, Biotechnol. Bioeng. 21:1121-1131 (1979)). They are generally referred to as "microbial polysaccharides" (Kirk-Othmer 15:439-447 (1981)). Synthesis occurs via dextransucrase enzymes which are primarily extracellular. Dextran molecular weights range from 1.5.times.10.sup.4 to 2.times.10.sup.7 and higher (Schwartz, R. D., and E. A. Bodie, Appl. Environ. Microbiol. 48:678-679 (1984)). Dextrans consist of primarily alpha 1,6 linkages but alpha 1,4, alpha 1,2 and alpha 1,3 bonds are also known (Niinobe, M. and T. Kobayashi, Nippon Nogeikagaku Kaishi 46:81-88 (1972)). The extent of branching affects water solubility and other properties. Dextrans are presently used in a variety of industries; however, although the potential exists, uses of dextrans in the food industry are limited at present because of the difficulty in providing a useful dried product which rehydrates in water to produce a suitably thick solution (Jeanes, A., ACS Symp. Ser. 45:284-298 (1977)).
Dextran synthesis has probably been most widely studied in the genera Leuconostoc, particularly in L. mesenteroides (Lawford, G. R., A. Kligerman, and T. Williams, Biotechnol. Bioeng. 21:1121-1131 (1979); Niinobe, M. and T. Kobayashi, Nippon Nogeikagaku Kaishi 46:81-88 (1972); and Preobrazhenskaya, M. E. and N. A. Danilova., Prikladnava Biokhimiva i Mikrobiologiya 10:539-546 (1974)). Leuconostoc sp. offer several advantages. First, they are unable to metabolize either dextrans (they contain no dextranases) or sucrose (no invertases or sucrose phosphorylases) (Jeanes, A. ACS Symp. Ser. 45:284-298 (1977)). Also, many Leuconostoc strains are prolific producers of sucrose-inducible extracellular dextransucrases and are, therefore, abundant producers of dextrans. Leuconostocs are used in foods. Finally, they are able to metabolize fructose, which is the byproduct of dextran synthesis, as an energy source. In some instances they can also produce levans (polyfructoses) by the action of levan sucrase.
Although dextrans presently have a variety of uses, few of these are in the food industry. One involves using dextran gel-filtration processes to concentrate or recover proteins from liquid wastes such as whey and cereal waste streams (Jeanes, A., ACS Symp. Ser. 45:284-298 (1977)).